Process of smelting ores containing zinc



No Model.) 4 -2 Sheets -Sheet 1. H. A. HUNIOKE. PROCESS OF SMELTING ORES CONTAINING ZINC. No. 487,444.

Patented Dec. 6, 1892.

(No Model.) 2 Sh etsSheet 2.

H. A. HUNIGKB.

PROCESS OF SMELTING ORBS CONTAINING ZINQ. No. 487,444. Patented Dec. 6, 1892.

UNITE STATES PAENT trace.

HENRY AUGUST HUNIOKE, OF ST. LOUIS, MISSOURI.

PROCESS OF SMELTING ORES CONTAINING ZINC.

SPECIFICATION forming part of Letters Patent No. 487,444, dated December 6, 1892.

Application filed August 21, 1890 Serial No. 362,671- (No specimens.)

To all whom it may concern.

Be it known that I, HENRY AUGUST HU- NIOKE, of St. Louis, Missouri, have made a new and useful Improvement in. Smelting Argentiferous or Auriferous Lead or Ferruginous Ores Containing Zinc, of which the following is a full, clear, and exact description.

The zincin the ores named is considered detrimental. Usually nothingis paid for the zinc contained in the ores, and, in fact, when the percentage of the zinc goes above a certain agreed percentage extra smelting charges are made, the charges increasing as the percentage increases.

The purpose of the present improvement is to provide for economically and eifectively treating ores such as namedthat is, to provide for smelting ores containing both lead and zinc with or without silver and gold or containing both iron and zinc. As the lastnamed combination is a simpler phase of the first named, (there being no necessity of providing for the collection of metal at thebot tom of the furnace,) it will suffice to explain the nature of the present process when ap plied to ores containing both lead and zinc with or without silver and gold.

The present improved process is based upon the following principle: Zinc oxide is reduced by carbonic oxide ata temperature above that at which zinebecomes volatile. Hence when zinc oxide is reduced by carbonic oxide the metallic zinc produced must always be in a volatile form. Now it appears that the zinc thus formed is exceedingly ready to re-enter into combination with oxygen not only in its free but also in its combined state. Therefore the metallic vapor if allowed to cool only inappreciably below its reduction temperature is quickly oxidized by carbonic acid or water. I utilize this fact in separating the zinc from the lead (therebyalso from silver or gold which remains with the lead when the lead is reduced) in such ores as above re-' ferred to. The theory of the present process will be more clearly understood by first noting the occurrences in a blast-furnace of the ordinary type. Leaving out all secondary elements of the nature of impurities of fuel (carbon) and the gangue of the zinc oxide, the case presents itself in its simplest form namely, as carbon and zinc oxide. When these elements are charged into a blast-furnace cold, they first become warmer by absorbing heat from the hot gases rising in the furnace. Descending more and more in the furnace they become hotter and hotter. Aside from such reactions as that of carbonic acid on carbon the carbon will remain unchanged until it reaches a zone where it finds free oxygen to combine with to form carbonic oxide. The zinc oxide continues to grow hotter and hotter until a zone is reached where the carbonic oxide formed in the furnace and continually surrounding the particles of zinc oxide can react on the zinc oxide, forming metallic zinc and carbonic acid. The moment the metallic zinc vapors are set free by this reaction they rise in company with all the other gases in the furnace, and in so doing they must of necessity pass through cooler zones, in which a reaction again occurs between the zinc vapors and the carbonic acid present, (more or less water also,) reconverting the zinc into zinc oxide. Instead, therefore, of getting metallic zinc there will be formed zinc oxide as the final reactionthat is, bringing the zinc oxide back into its original form. The result of this simple blastfurnace procedure would thus be equivalent to the combustion of carbon simply. That such a process could be of value practically can safely be doubted, for the zinc oxide produced, although in a fine state of division and in part carried off by the gases, will largely be retained mechanically by the superincumbent layers of the charge and be brought down again to the-zone of reduction, where again being reduced it rises and again is oxidized. Thus there isa gradual accumulation of zinc oxide to such an extent that complete reduction is impossible, and it is even found that the furnace chills completely unless provision is made to drive all the zinc oxide into the slag. Now to obviate this difficultyl heat both the carbon and the zinc oxide,but sepa rately from each other and to at least the temperature at which carbonic oxide reduces zinc oxide, and I charge the blast-furnace with this preheated material, and the result is that when the zinc oxide is reduced to zinc it is free to move with the other gases, and it is immediately drawn off through an escapefi ue, even though it may have been partly acted upon by the other gases and have been converted into zinc oxide the moment it leaves the furnace. In any eventit istakenawayfrom the X0 furnace. The hotter the material is charged into the furnace the more perfectly does the zinc leave the furnace. In applying this process to an ore containing both lead and zinc it is found that the reduced zinc leaves the blast-furnace through a due, (arranged for the purpose,) while the reduced lead, it being nonvolatile in the metallic state, sinks through the charge of the furnace to the bottom thereof. It is necessary for the purposes of this process that the lead and zinc be delivered into the furnace in the form of oxides. Hence when sulphides are to be treated it is necessary to roast them, thereby driving off all of the contained sulphur. When the roasting 2 5 operation is completed, the ore will have acquired a high temperature. Thisheat is used in preference to one obtained by means of a special heating. The ore when drawn from the roasting-furnace is as quickly as pos- 0 sible charged into the blast-furnace. It is convenient to have at least two roasting-furnaces to each blast-furnace, and it is also advantageous to introduce soakingpits between the roasting and blast furnaces for the pur- 5 pose of maintaining the supply of hot ore.

Such soaking-pits can be placed directly under the lasthearth of the roasting-furnace and be simply chambers of fire-brick or other non-heat-conducting and fireproof material. The ore when drawn from the roasting-furnaces or soaking-pits is weighed before it is delivered into the blast-furnace. The fuel for the blast-furnace is heated separatelysay in a shaft-furnace provided with a grate 5 at the bottom and with a charging-door and stack at the top. The fuel is drawn out hot from 0d the grate and into a receptacle-say a basket-of definite size, thereby to enable the supply to be regulated, and it is then dumped into the blast-furnace. This charge of hot ore and hot fuel is acted upon almost immediately after it enters the blast-furnace and the zinc oxide and lead oxide are reduced to the metallic state, the lead going to the bottonrof the furnace, carrying thesilver and gold with it, while the zinc leaves the furnace through the described escape-flue, whence it is conducted to cooling-chambers and there allowed to cool. The cooling of 6c the zinc vapors necessitates their oxidation in presence of gases of combustion, and it is only necessary to apply these vapors to the largest cooling-surface to enable them to deposit completely. When the roasting of the ore has been completein other words, when the sulphur has been driven out of the ore in the roasting process and any appreciable amount of sulphur is avoided in the charge which is delivered into the blast-furnacea comparatively-pure zinc is formed.

In spite of its purity it is not well adapted to pigment purposes and it is more properly charged into retorts of usual design and therein distilled to form spelter.-

The most desirable means for carrying out the present process is exhibited in the annexed drawings, making part of this specification, in whicl Figure 1 is a general plan, and Fig. 2 a side elevation, of the plant; Fig. 3, a vertical section of the plant, omitting the roasting-furnaces, the section being taken on the line 3 3 of Fig. 4, which in turn is a horizontal section on the line 4 4 of Fig. 3.

The last two named views are upon an enlarged scale.

The same letters of reference denote the same parts.

A A represent the ore-roasting furnaces. Each furnace may have any desirable number of hearths a a.

13 represents the f uel-heatin g furnace. oreroasting furnaces and the f uel-heating furnace are on the same higher level. blast-furnace G is arranged at a lower level, so that its top 0 is at the general level of the bottom of the furnaces A B. Special features of the blast-furnace are the lid or bell c for closing the furnace-top and the escape-flue 0 leading out of the furnace just below the level of the bell and about five or five and one-half feet above the tuyeres c otherwise the blast-furnace is of the usual design, saving that it is cut off about seven feet above the tuyeres, the object being to confine the reducing operation and slag formation to the blast-furnace and to efiect the heating up of the ore and fuel in the other furnaces A B. The lead is caught in a basin D at the bottom of the blast-furnace and in the customary manner. The roasted ore is'conveniently delivered to the blast-furnace by means of cars E E, moved upon trackways e 6, leading past the roasting-furnaces to the top of the last furnace G. The fuel, which has been charged into the furnace B through its doorway I), is supported while being heated upon the grate b. F represents the basket into which the fuel is drawn from off the grate b and which serves by being tilted upon its pivot f, as indicated by the broken lines in Fig. 3, to deliver the fuel to the blast-furnace. The gases generated in the blast-furnace and containing the zinc vapor already partially oxidized escape from the blast-furnace through the flue a into a chamber. G, where the coarser dustsuch as fine ore and coke-dustseparates from them. The gaseous currents pass from the chamber G, into one or the other of the tines H H. To

control the direction of the current, valves I 1' are arranged, substantially as shown, be-

The.

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tween the chamber G and the fines H H, respectivelythat is, the flues H H are used alternately, and as one is being used the other may be opened for the purpose of cleaning it, and when the last-named one is being used as a flue the first-named is similarly cleaned. The dust-chamber G is built substantially in the form shown, audit is provided with partitions, which extend part way across the chamber, substantially as shown at g g, for the purpose of protecting the valves I I from the direct action of the hot current. At the other end of the flues H H, respective ly, are two other valves, (not shown,) which are used in conjunction with the valves I I, respectively, for the purpose of shutting ofi the fines H H alternately. The fines in question terminate in a common stack. (Not shown.) The fines H H have openings h h at the side thereof, Which are closed by doors until it is desired to open the tines for the purpose described. The principal thing to be considered in designing the tines described is the obtaining of the largest possible cooling-surface for the deposition of the zinc. The larger the area of cooling-surface the better the result. In the event the ore treated does not require to be roasted it must be heated spevionsly-roasted ores and the fuel, but separately from each other and respectively in separate furnaces, to at least the temperature at which carbonic oxide reduces zinc oxide, then charging said preheated ore and fuel into a blast-furnace, and after so introducing said charge of preheated ore and fuel maintaining it at all parts thereof at said temperature and carrying off the zinc and discharging it in a volatile form through an escapeflue at the upper part of said blast-furnace into a separate chamber and simultaneously reducing and collecting the principal metal or metals of said ores at the bottom of said furnace.

Witness my hand this 16th day of August,

HENRY AUGUST HUNICKE.

Witnesses:

O. D. MOODY, B. F. REX. 

